1. Field of the Invention
This invention relates to certain 4-methoxybiphenyl hydrazide derivatives useful as intermediates in the preparation of isopropyl-2-(4methoxy-[1,1xe2x80x2-biphenyl]-3-yl)hydrazine carboxylate (Bifenazate).
2. Description of Related Art
Destruction by insects, acarids and nematodes presents a serious problem to agriculture. A wide variety of field crops are in need of protection from nematodes, acarids, and insects, including such valuable crops as soybeans, corn, peanuts, cotton, alfalfa, rice, and tobacco. In addition, vegetables, such as tomatoes, potatoes, sugar beets, carrots, peas, and the like, as well as fruits, nuts, ornamentals, and seed bed crops, such as apples, peaches, almonds, citrus fruit, and grapes may also require protection from the ravages of such pests.
Consequently, the development of new, more effective methods for preparing known pesticides, including insecticides, acaricides, and nematicides represents an ongoing scientific activity. More particularly, the development of improved methods for the preparation of known pesticides that are effective as both ovicides and larvicides are of interest.
One such pesticide is Bifenazate, which can be prepared by a six step procedure from 4-hydroxybiphenyl hydrazine, which is, in turn, prepared from a diazonium salt. This method is laborious, costly, and requires careful attention to the sensitive key steps, i.e., the preparation and reduction of the diazonium salt.
U.S. Pat. No. 5,367,093 describes a method for the preparation of the miticidal phenylhydrazine derivative, isopropyl-2-(4methoxy-[ 1,1xe2x80x2-biphenyl]-3-yl)hydrazine carboxylate (bifenazate), using a six-step procedure comprising the undesirable steps of preparation and reduction of a diazoniun salt.
U.S. Pat. No. 6,093,843 discloses compounds having the formula: 
wherein R is hydrogen or CO2CH(CH3)2, useful as intermediates in the preparation of the miticide bifenazate, methods for their preparation, and methods for the preparation of the bifenazate.
U.S. Pat. No.6,235,936 discloses a method for the transition metal-catalyzed arylation, or vinylation, of hydrazines, hydrazones, and the like. Additionally, a strategy is provided, the cornerstone of which is a transition metalatalyzed arylation or vinylation method, for the synthesis of indoles, carbazoles, and the like. It is said that the methods and strategies of the invention may be utilized in standard, parallel, and combinatorial synthetic protocols. (See also the related WO 99/43643 and Wagaw et al., J. Am. Chem. Soc. 120(26):6621-2 (1998).)
Additionally, certain phenylhydrazine derivatives can be prepared using the methods described in U.S. Pat. No. 4,864,032 (amination of Grignard); in Mitchell, J. Org. Chem. 59: 682 (1994) (amination of electron-rich arenes); and in Lenarsic, J. Org. Chem. 64: 2558 (1999) (by electrophilic azodicarboxylates).
The disclosures of the foregoing are incorporated herein by reference in their entirety.
It is an object of the present invention to provide new intermediates useful in the preparation of bifenazate.
It is another object of the present invention to provide a new method for the preparation of bifenazate.
It is another object of the present invention to prepare aryl hydrazones of 4-alkoxybiphenyl that are useful as intermediates for the preparation of bifenazate, whereby the inefficient preparation and reduction of a diazonium salt intermediate can be avoided.
These and other objects are accomplished by means of the present invention, which relates to compounds (hereinafter referred to as Compound I) that are useful intermediates for the preparation of bifenazate having the formula: 
wherein R1 is alkyl and R2 and R3 are independently selected aryl groups.
Thus, the present invention is directed to a compound having the formula: 
wherein R1 is alkyl and R2 and R3 are independently selected aryl groups.
In another aspect, the present invention is directed to a method for preparing bifenazate comprising:
A) coupling a 3-halo-4-methoxybiphenyl, preferably 3-bromo-4-methoxybiphenyl, with a diarylhydrazone in the presence of a coupling catalyst, a ligand, a first base, and a solvent at or above room temperature to form a compound of the formula I: 
B) treating the compound of formula I with a mixture of hydrochloric acid and ethyl acetate to give a compound of formula II: 
C) converting the compound of formula II to bifenazate by reaction with an alkali metal hydroxide, preferably sodium hydroxide, followed by reaction with an isopropyl haloformate, preferably isopropyl chloroformate, in the presence of a second base.
As disclosed above, the present invention relates to compounds having the formula: 
wherein R1 is alkyl and R2 and R3 are independently selected aryl groups.
R1 is preferably a lower alkyl, which may, if desired, be branched. It is more preferably a lower alkyl of from one to four carbon atoms, e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl. Thus, OR1 in the above formula will be an alkoxy group, preferably methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, or tert-butoxy. It is especially preferred that R1 be methyl and OR1 be methoxy.
R2 and R3 of Compound I are independently selected aryl groups, which may be substituted or unsubstituted. The term xe2x80x9carylxe2x80x9d as used herein includes 5-, 6- and 7-membered single-ring aromatic groups that may include from zero to four heteroatoms, for example, benzene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine, pyriridine, and the like. Those aryl groups having heteroatoms in the ring structure may also be referred to as xe2x80x9caryl heterocyclesxe2x80x9d or xe2x80x9cheteroaromaticsxe2x80x9d. The aromatic ring can be substituted at one or more ring positions with such substituents as, for example, halogen, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, nitro, alkylthio, heterocyclyl, aromatic or heteroaromatic moieties, -CF3, -CN, or the like. The term xe2x80x9carylxe2x80x9d also includes polycyclic ring systems having two or more cyclic rings in which two or more carbons are common to two adjoining rings (the rings are xe2x80x9cfused ringsxe2x80x9d) wherein at least one of the rings is aromatic, e.g., the other cyclic rings can, if desired, be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls, and/or heterocyclyls.
It is preferred that both R2 and R3 be phenyl, either or both of which can optionally be substituted, preferably with one or more groups selected from the group consisting of halo, alkoxy, haloalkyl, thienyl, fluorenyl, and halofluorenyl.
The compounds employed in the practice of the present invention can be prepared as described below and as shown in Scheme 1. 
3-Bromo4-methoxybiphenyl is coupled with a diarylhydrazone using a suitable coupling catalyst in the presence of a suitable ligand and a base in a suitable solvent at room or elevated temperature to form Compound I.
The coupling catalyst is preferably a transition metal catalyst including soluble or insoluble complexes of platinum, palladium, and nickel. Nickel and palladium are particularly preferred and palladium is most preferred. Suitable catalysts include, but are not limited to, palladium acetate, tris(dibenzylideneacetone)dipalladium, nickel diphenylphosphinoferrocene, and the like.
The ligand is preferably a phosphine ligand that is commercially available or can be prepared by methods similar to processes known in the art. The phosphines can, for example, be tri-tert-butylphosphine, 2-(di-tert-butylphophino)biphenyl, 2,2-xe2x80x2(dicyclohexylphosphino)biphenyl, or a bidentate phosphine ligand, such as 2,2xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-binaphthyl, 1,2-bis(dimethylphosphino)ethane, 1,2-bis(diethylphosphinoethane, 1,2-bis(dipropylphosphino)ethane, 1,2-bis(diisopropylphosphino)ethane, 1,2-bis(dibutyl-phosphinocthane, 1,2-bis(dicyclohexylphosphino)ethane, 1,3-bis(dicyclohexylphosphino)propane, 1,3-bis(diiso-propylphosphino)propane, 1,4-bis(diisopropylphosphino)-butane, or 2,4-bis(dicyclohexylphosphino)pentane.
Bis(phosphine) ligands are particularly preferred. Suitable bis(phosphine) compounds include, but are not limited to, (xc2x1)-2,2xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-binaphthyl (and separate enantiomers), (xc2x1)-2,2xe2x80x2-bis(di-p-tolylphosphino)-1,1,xe2x80x2-binaphthyl (and separate enantiomers), 1,1xe2x80x2-bis(diphenylphosphino)ferrocene, 1,3-bis(diphenylphosphino)propane, 1,2-bis(diphenylphosphino)benzene, 2,2xe2x80x2-bis(diphenylphosphino)diphenyl ether, and 1,2-bis(diphenylphosphino)ethane.
The most preferred ligands for use in the practice of the present invention include 2,2xe2x80x2-bis(diphenylphosphino)-1,1xe2x80x2-binaphthyl, bis {2-(diphenylphosphino)phenyl}ether, 1-(N,N-dimethylamino)-1xe2x80x2-(dicyclohexylphosphino)biphenyl, 1,1xe2x80x2-bis(diphenylphosphino)ferrocene, and the like.
The base employed in the coupling reaction can, for example, be an alkoxide, such as alkali metal alkoxides, e.g., sodium tert-butoxide; an alkali metal or alkaline earth carbonate or phosphate (e.g. sodium, magnesium, calcium, barium, potassium carbonate or phosphate). Preferred bases for use in the practice of the present invention include sodium t-butoxide, cesium carbonate, and potassium phosphate.
Suitable solvents include ethers, such as diethyl ether, 1,2-dimethoxyethane, diglyme, t-butyl methyl ether, tetrahydrofuiran, and the like; halogenated solvents, such as chloroform, dichloromethane, dichloroethane, chlorobenzene, and the like; aliphatic or aromatic hydrocarbon solvents, such as benzene, xylene, toluene, hexane, pentane, and the like; esters and ketones, such as ethyl acetate, acetone, and 2-butanone; polar aprotic solvents, such as acetonitrile, dimethylsulfoxide, dimethylformamide, and the like; or combinations of two or more solvents. Toluene, dimethoxyethane, and tetrahydrofuran are preferred.
In general, it will be desirable that the coupling reaction be run using mild conditions that will not adversely affect the reactants, the catalyst, or the product. The coupling reaction will usually be run at temperatures ranging from room temperature, e.g., about 20xc2x0 C., to about 300xc2x0 C., preferably from about 200xc2x0 C. to about 150xc2x0 C.
Compound I can then be treated with a mixture of hydrochloric acid and ethyl acetate to give hydrazine intermediate II , which can be converted to bifenazate by reaction with sodium hydroxide followed by reaction with isopropyl chloroformate in the presence of a base, e.g., pyridine. Compound II is an intermediate in a known method for preparing bifenazate, and the method for its conversion to bifenazate is described in U.S. Pat. No. 5,367,093.